From 96204afa0954ce68a0354e7eee74853e4421d1d1 Mon Sep 17 00:00:00 2001
From: bdemsky <bdemsky>
Date: Fri, 3 Feb 2006 01:14:13 +0000
Subject: [PATCH] checking in cup

---
 Robust/cup/CHANGELOG     |  313 ++++++++
 Robust/cup/INSTALL       |  107 +++
 Robust/cup/INSTALL.QUICK |   17 +
 Robust/cup/LICENSE       |   20 +
 Robust/cup/README        |   48 ++
 Robust/cup/cup_logo.gif  |  Bin 0 -> 8054 bytes
 Robust/cup/manual.html   | 1452 ++++++++++++++++++++++++++++++++++++++
 7 files changed, 1957 insertions(+)
 create mode 100644 Robust/cup/CHANGELOG
 create mode 100755 Robust/cup/INSTALL
 create mode 100644 Robust/cup/INSTALL.QUICK
 create mode 100644 Robust/cup/LICENSE
 create mode 100644 Robust/cup/README
 create mode 100644 Robust/cup/cup_logo.gif
 create mode 100644 Robust/cup/manual.html

diff --git a/Robust/cup/CHANGELOG b/Robust/cup/CHANGELOG
new file mode 100644
index 00000000..5365a357
--- /dev/null
+++ b/Robust/cup/CHANGELOG
@@ -0,0 +1,313 @@
+CUP version 0.10k is a maintenance release.
+
+CUP will now accept a filename on the command-line if it is the last
+argument and does not start with "-".  This allows better GUI
+integration.  Some unix-isms in end-of-line handling have been fixed,
+too; thanks to Jean Vaucher <vaucher@iro.umontreal.ca> for the tip.
+
+The java_cup.runtime.Scanner interface has been refined to allow
+the scanner to return null to signal EOF.  JLex and JFlex users will
+like this, as it means they can use the default scanner EOF behavior.
+
+Bruce Hutton <b_hutton@cs.auckland.ac.nz>, Zerksis Umrigar <zdu@acm.org>,
+and Vladimir Antonevich <Vladimir.Antonevich@solcorp.com> all sent bug
+reports touching on erroneous error recovery in the parser runtime.
+Dr. Hutton provided the fixes that I've adopted; Zerksis sent a very
+helpful CUP-vs-bison test case.  If you're in a position to notice
+correct/incorrect error recovery and this release works better for you
+than previous ones, thank them --- and send me email so I know whether
+we've quashed this bug for good.
+
+Klaus Georg Barthelmann <barthel@Informatik.Uni-Mainz.DE> caught an
+oversight in the constructors for java_cup.runtime.Symbol.  I've also
+taken an obsolete constructor allowing specification of a start state
+for some symbol to package-scope; if this causes anyone backwards
+compatibility problems, email me and I will consider changing it back.
+
+C. Scott Ananian
+Laboratory for Computer Science
+Massachusetts Institute of Technology
+Jul-24-1999 [CSA]
+------------------------------------------------------------------------
+CUP version 0.10j adds new features.
+
+A "-version" command-line option is now accepted, which prints out the
+working version of CUP and halts.  This allows automatic version-checking,
+for those applications which require it.
+
+Broadened the CUP input grammar to allow CUP reserved words in package and
+import statements, and in (non)terminal labels. In addition, semicolons
+after 'action code', 'parser code', 'init code', and 'scan with' sections
+have been made optional (if language noise annoys you).  Also, these four
+sections may now appear in any order, instead of the strict ordering
+previously required.  Finally, you can now spell 'non-terminal' as either
+"non terminal" (old way) *or* "nonterminal" without upsetting CUP.
+[Flexibility requested by Stefan Kahrs <S.M.Kahrs@ukc.ac.uk>]
+[Package and import reserved word issues noted by Frank Rehberger,
+ Brandon Schendel, and Bernie Honeisen, among others.]
+
+Clarified the parse table dumps generated by the -dump* options.
+
+I have added code to lr_parser to detect illegal Symbol recycling by the
+scanner and to throw an Error in this case.  The scanner must return
+a fresh Symbol object on each invocation, because these objects are
+tagged with parse state and added to the parse stack.  Object sharing
+does evil things to the parser; don't do it (you won't get away with it).
+[Symbol recycling problems reported by Ken Arnold <Ken.Arnold@Sun.COM>]
+
+Improved scanner interface, designed by David MacMahon <davidm@smartsc.com>.
+The new java_cup.runtime.Scanner interface is used by the default
+implementation of lr_parser.scan().  See the manual for more details.
+Old parsers will work with the new runtime, but parsers generated with
+0.10j will not work with the runtime from earlier versions unless you
+specify the (new) "-noscanner" option.
+
+C. Scott Ananian
+Laboratory for Computer Science
+Massachusetts Institute of Technology
+Jul-24-1999 [CSA]
+------------------------------------------------------------------------
+CUP version 0.10i is a maintenance release.
+
+A one-off bug in the parser error-recovery code has been caught and corrected
+by Chris Harris <ckharris@ucsd.edu>.
+
+The fields in the emitted symbol class have been made public, rather than
+package scope, since the class already was public.
+
+The issues formerly addressed in Appendix D (accessing parser methods/fields
+from the action class) have been partially addressed by adding a new
+private final field named 'parser' to the action object that points to
+the parser object.  THIS INTRODUCES A POTENTIAL INCOMPATIBILITY if you had
+previously defined a field named 'parser' in the 'action code {: ... :}'
+portion of your grammar.  The solution is to rename your field.
+
+Finally, incorporated Jako Andras' suggestions to make CUP more friendly
+to makefiles.
+
+A reminder: please submit bug-fixes or feature-additions as *patches*, not
+complete archives.  Your patch will have a greater chance of integration
+into the distribution if you package each feature or fix as a separate patch,
+instead of lumping everything together and leaving it to me to figure out
+what you've changed and why.
+
+C. Scott Ananian
+Laboratory for Computer Science
+Massachusetts Institute of Technology
+Feb-18-1999 [CSA]
+------------------------------------------------------------------------
+CUP version 0.10h is a maintenance release.
+
+Starting with this version, CUP encodes the various parser tables as strings
+to get around java's 64k method-size limitation.  This allows larger
+parse tables and thus more complicated grammars.
+
+Furthermore, a long-standing buglet that would cause CUP to occasionally
+generate "Attempt to construct a duplicate state" internal errors has been
+fixed.
+
+Another contributed Microsoft-compatible makefile has also been added
+to the distribution.
+
+C. Scott Ananian
+Laboratory for Computer Science
+Massachusetts Institute of Technology
+Feb-10-1999 [CSA]
+------------------------------------------------------------------------
+CUP version 0.10g contains bug fixes, added functionality, and
+performance improvements.  Thanks to Matthias Zenger, Peter Selinger,
+Jaroslaw Kachinarz, Ian Davis and others for contributions.
+
+- New command line option '-interface' added.  This causes JavaCUP to
+  emit an *interface* with the symbol constants, instead of a
+  *class*.  Without the command-line flag, behavior is identical to
+  v0.10f and before: the symbols are emitted as a class.
+- (minor) Added toString() method to java_cup.runtime.Symbol and
+  modified the debugging parser to use it.  This allows you to
+  override toString() to allow a more intelligible debugging parse.
+- The CUP grammar has been extended to allow one to declare array types
+  for javaCUP terminals and non-terminals.  Matthias Zenger first 
+  suggested this feature; Peter Selinger was the first to show the
+  right way to do it.
+- The symbols prefixed with CUP$ now have the parser class file name 
+  added to the prefix as well, to allow more than one parser object
+  per package.  Thanks to Jaroslaw Kachniarz for pointing out this
+  problem.
+- Fixed bug that prevented one from invoking the parser multiple times.
+  To quote Ian Davis, who found and diagnosed the bug:
+    Repeat invocations of the same instantiation of lr_parser.java to parse
+    distinct input statements fail for the simple reason that the stack is
+    not emptied at start of parsing, but the stack offset is reset to 0.
+  This has been fixed.
+- Fixed bug with implicit start productions not receiving a RESULT.
+- Fixed bug with RESULT assignments that are not right-most in the
+  production.
+- Updated documentation.
+
+Known issues:
+- All known bugs have been fixed.
+- The java_cup.runtime.SymbolStack / java_cup.runtime.intStack
+  performance hack originally suggested by Matthias Zenger has been
+  postponed to the next release.  By eliminating typecasts and 
+  synchronized methods, a substantial performance improvement can be 
+  obtained.  Backwards-compatibility issues have forced the postponement 
+  of the code merge.
+
+C. Scott Ananian
+Laboratory for Computer Science
+Massachusetts Institute of Technology
+3/24/98 [CSA]
+------------------------------------------------------------------------
+CUP version 0.10f is a maintenance release.  The code has been cleaned up
+for JDK 1.1 functionality. No major functionality has been added; any bugs
+in 0.10e are still in 0.10f.
+
+- Removed trailing semicolons from class definitions which upset strict
+  compilers (not Sun's javac, for some reason).
+- Changed 'PrintStream's to 'PrintWriter's to eliminate deprecation 
+  warnings.
+
+As of this release, the javaCUP code is being maintained by
+C. Scott Ananian.  Suggestions and bug-fixes should be sent to
+cananian@alumni.princeton.edu. 
+
+Known issues:
+
+- Precedence bug: rules unmarked by precedence information are treated
+  as if they had existing, but very low, precedence.  This can mask
+  parser conflicts.
+- Efficiency hack: java.util.Stack will be replaced in the next
+  release with a special-purpose stack to eliminate
+  performance-robbing type-casts.
+- It has been suggested that the symbol *class* should be an
+  *interface* instead.  This will be a command-line option in the next
+  release. 
+
+C. Scott Ananian
+Laboratory for Computer Science
+Massachusetts Institute of Technology
+12/21/97 [CSA]
+------------------------------------------------------------------------
+CUP version 0.10e contains a few bug fixes from 0.10a
+
+- %prec directive now works correctly 
+	fixed by cananian@princeton.edu <C. Scott Ananian>
+- Shift reduce conflicts are now correctly reported
+	fixed by danwang@cs.princeton.edu <Daniel . Wang>
+- Error with reporting the positon of the error token also fixed
+	fixed by cananian@princeton.edu <C. Scott Ananian>
+- INSTALL script now has a slightly more complex test.
+- foo.java.diff included for changes from previous release
+- Fixed more bugs with reporting of shift reduce conflicts.
+	fixed by danwang@cs.princeton.edu <Daniel . Wang>
+- Fixed bug introduced by previous fix patches from <hosking@.cs.purdue.edu>
+  Added '\r' as a whitespace character for the lexer suggested by 
+	(dladd@spyglass.com)
+- Fixed botched relase
+Daniel Wang
+Department of Computer Science
+Princeton University
+
+Last updated:  9/12/97 [DW]
+------------------------------------------------------------------------
+Changes and Additions to CUP v0.9e
+
+CUP version 0.10a is a major overhaul of CUP.  The changes are severe,
+meaning no backwards compatibility to older versions.
+
+Here are the changes:
+
+1.  CUP now interfaces with the lexer in a completely different
+manner.  In the previous releases, a new class was used for every
+distinct type of terminal.  This release, however, uses only one class:
+The Symbol class.  The Symbol class has three instance variables which 
+are significant to the parser when passing information from the lexer.
+The first is the value instance variable.  This variable contains the 
+value of that terminal.  It is of the type declared as the terminal type
+in the parser specification file.  The second two are the instance
+variables left and right.  They should be filled with the int value of
+where in the input file, character-wise, that terminal was found.
+
+2. Terminal and non-nonterminal declarations now can be declared in two
+different ways to indicate the values of the terminals or non-terminals.
+The previous declarations of the form
+
+terminal {classname} {terminal} [, terminal ...];
+
+still works.  The classname, however indicates the type of the value of
+the terminal or non-terminal, and does not indicate the type of object
+placed on the parse stack.
+
+A declaration, such as:
+
+terminal {terminal} [, terminal ...];
+
+indicates the terminals in the list hold no value.
+
+3. CUP doesn't use the Symbol class for just terminals, but for all
+non-terminals as well.  When a production reduces to a non-terminal, a
+new Symbol is created, and the value field is filled with the value of
+that non-terminal.  The user must know that the terminal and non terminal
+declarations specify a type corresponding to the type of the value field
+for the symbol representing that terminal or non-terminal.
+
+4. Label references do not refer to the object on the parse stack, as in
+the old CUP, but rather to the value of the value instance variable of
+the Symbol that represents that terminal or non-terminal.  Hence,
+references to terminal and non-terminal values is direct, as opposed to
+the old CUP, where the labels referred to objects containing the value
+of the terminal or non-terminal.
+
+5. The RESULT variable refers directly to the value of the non-terminal
+to which a rule reduces, rather than to the object on the parse stack.
+Hence, RESULT is of the same type the non-terminal to which it reduces, 
+as declared in the non terminal declaration.  Again, the reference is
+direct, rather than to something that will contain the data.
+
+6. For every label, two more variables are declared, which are the label
+plus left or the label plus right.  These correspond to the left and
+right locations in the input stream to which that terminal or
+non-terminal came from.  These values are propagated from the input
+terminals, so that the starting non-terminal should have a left value of
+0 and a right value of the location of the last character read. 
+
+7. A call to parse() or debug_parse() return a Symbol.  This Symbol is
+of the start non-terminal, so the value field contains the final RESULT
+assignment. 
+
+8. CUP now has precedenced terminals.  a new declaration section,
+occurring between the terminal and non-terminal declarations and the
+grammar specifies the precedence and associativity of rules.  The
+declarations are of the form:
+
+precedence {left| right | nonassoc} terminal[, terminal ...];
+...
+
+The terminals are assigned a precedence, where terminals on the same
+line have equal precedences, and the precedence declarations farther
+down the list of precedence declarations have higher precedence.  left,
+right and nonassoc specify the associativity of these terminals.  left
+associativity corresponds to a reduce on conflict, right to a shift on
+conflict, and nonassoc to an error on conflict.  Hence, ambiguous
+grammars may now be used.  For a better explanation, see the manual.
+
+9.  Finally the new CUP adds contextual precedence.  A production may be
+declare as followed:
+
+lhs ::= {right hand side list of terminals, non-terminals and actions}
+        %prec {terminal};
+
+this production would then have a precedence equal to the terminal
+specified after the "%prec".  Hence, shift/reduce conflicts can be
+contextually resolved.  Note that the "%prec terminal" part comes after
+all actions strings.  It does not come before the last action string.
+
+For more information read the manual, found in manual.html
+
+Frank Flannery
+Department of Computer Science
+Princeton University
+
+Last updated:  7/3/96 [FF]
+
+
diff --git a/Robust/cup/INSTALL b/Robust/cup/INSTALL
new file mode 100755
index 00000000..49708521
--- /dev/null
+++ b/Robust/cup/INSTALL
@@ -0,0 +1,107 @@
+#!/bin/csh -f
+#
+# Cup install and test script
+# Scott Hudson 8/31/95
+#  
+# Last revision 7/3/96 (for v0.10a)
+# By Frank Flannery
+#
+# Last revision 11/16/96 (for v0.10b)
+# By Daniel Wang
+#
+# Updated version number 7/24/99 for 0.10k
+# By C. Scott Ananian
+echo 
+echo "================================"
+echo "Installing and testing Cup v0.10k"
+echo "================================"
+echo
+
+# check for this directory in CLASSPATH 
+#
+set cwd = `pwd`
+set c_path = `printenv CLASSPATH`
+if ($c_path !~ "*$cwd*") then
+  echo " "
+  echo "WARNING:"
+  echo "WARNING: The current directory does not appear in your CLASSPATH"
+  echo "WARNING: it will be added for this install/test only"
+  echo "WARNING:"
+  echo " "
+  setenv CLASSPATH $cwd':'$c_path
+  echo "CLASSPATH now set to " 
+  printenv CLASSPATH
+endif
+  
+# change to the demo directory
+#
+echo " "
+echo "changing to simple_calc subdirectory..."
+echo "cd java_cup/simple_calc"
+cd java_cup/simple_calc 
+
+# remove old copies of parser.java and sym.java
+#
+echo " "
+echo "removing any old copies of parser.java and sym.java..."
+echo "rm -f parser.java sym.java"
+rm -f parser.java sym.java
+
+# compile java_cup and run it against the demo program
+#   the -cs (for "checksource") option here will force the 
+#   java_cup and java_cup.runtime source to be compiled prior 
+#   to running it.
+#
+echo " "
+echo "compiling java_cup then generating demo program..."
+echo "java -cs java_cup.Main < parser.cup"
+java -cs java_cup.Main < parser.cup 
+
+# make sure parser.java and sym.java now exist
+#
+if ( ! -e parser.java) then
+  echo " "
+  echo "ERROR: for some reason parser.java was not created"
+  echo "ERROR: install was not successful"
+  exit 1
+endif
+if ( ! -e sym.java) then
+  echo " "
+  echo "ERROR: for some reason sym.java was not created"
+  echo "ERROR: install was not successful"
+  exit 1
+endif
+
+# run the demo
+#  again, the -cs option will cause compilation of all the parts 
+#  of the demo program (including parser.java and sym.java that 
+#  should have been generated in the previous step).
+#
+echo "removing old test results..."
+echo "rm -f test_results"
+rm -f test_results
+echo " "
+echo "executing the demo program..."
+echo "echo '1*-2+2;' | java -cs java_cup.simple_calc.Main >& test_results"
+echo '1*-2+2;' | java -cs java_cup.simple_calc.Main >& test_results
+
+# compare with standard results 
+#
+set res = `tail -1 test_results`
+if ("$res" !~ "= 0") then
+  echo "ERROR: test program produced the wrong results"
+  echo "ERROR: output was:"
+  cat test_results
+  echo "ERROR: install was not successful"
+  rm -f test_results
+  exit 2
+endif
+  
+# all is well
+#
+rm -f test_results
+echo " "
+echo "=============================="
+echo "Install and test was successful"
+echo "=============================="
+exit 0
diff --git a/Robust/cup/INSTALL.QUICK b/Robust/cup/INSTALL.QUICK
new file mode 100644
index 00000000..bf708b67
--- /dev/null
+++ b/Robust/cup/INSTALL.QUICK
@@ -0,0 +1,17 @@
+This is a quick installation guide for the CUP system.
+For most people, the following steps will suffice:
+
+ 1) extract the java_cup files somewhere, and ensure that
+    the extraction directory is in your classpath.
+
+    This will ensure that java_cup.Main properly refers to the
+    Main class in the java_cup subdirectory of this release.
+
+ 2) compile java_cup and its runtime system.
+    From the installation directory:
+      javac java_cup/*.java java_cup/runtime/*.java
+
+That's it!  Read the manual now.
+  --Scott 
+
+24-Mar-1998
diff --git a/Robust/cup/LICENSE b/Robust/cup/LICENSE
new file mode 100644
index 00000000..f3f0299f
--- /dev/null
+++ b/Robust/cup/LICENSE
@@ -0,0 +1,20 @@
+CUP PARSER GENERATOR COPYRIGHT NOTICE, LICENSE AND DISCLAIMER.
+
+Copyright 1996 by Scott Hudson, Frank Flannery, C. Scott Ananian
+
+Permission to use, copy, modify, and distribute this software and its
+documentation for any purpose and without fee is hereby granted,
+provided that the above copyright notice appear in all copies and that
+both the copyright notice and this permission notice and warranty
+disclaimer appear in supporting documentation, and that the names of
+the authors or their employers not be used in advertising or publicity 
+pertaining to distribution of the software without specific, written 
+prior permission.
+
+The authors and their employers disclaim all warranties with regard to 
+this software, including all implied warranties of merchantability and 
+fitness.  In no event shall the authors or their employers be liable 
+for any special, indirect or consequential damages or any damages 
+whatsoever resulting from loss of use, data or profits, whether in an 
+action of contract, negligence or other tortious action, arising out of 
+or in connection with the use or performance of this software.
diff --git a/Robust/cup/README b/Robust/cup/README
new file mode 100644
index 00000000..58bacd79
--- /dev/null
+++ b/Robust/cup/README
@@ -0,0 +1,48 @@
+This directory contains the CUP v0.10k release in source form.  You should
+find the following files and subdirectories in this release:
+
+  README            This file.
+  INSTALL.QUICK     Quick installation instruction.
+  CHANGELOG         A brief overview of the changes in v0.10k
+  java_cup          A subdirectory containing CUP, runtime, and test sources.
+  cup_logo.gif      A logo image used by the manual.
+  manual.html       A user's manual in HTML format. (OLD)
+  INSTALL           A shell script to install and test the system
+
+To get started quickly, read INSTALL.QUICK.  If you are on a Windows
+platform, you might want to look in the winnt subdirectory.
+For complete installation information, keep reading.
+
+To install the release, copy the contents of this directory (if you
+haven't done so already) into a "classes" directory accessible to the
+java interpreter (i.e., a directory that is listed in the colon
+separated list of directories in your CLASSPATH environment variable).
+Note: if you have an older version of the system already accessible
+from your CLASSPATH you will want to temporarily remove it to avoid
+conflicts.
+
+Once files have been copied to an appropriate location, you should be able to
+both compile and test the system by executing the INSTALL shell script
+(sorry, but non Unix users are still on their own).  Again, be sure that 
+you have placed these sources in a directory listed in your CLASSPATH 
+environment variable (or changed your CLASSPATH to include this directory).  
+
+A manual page that explains the operation and use of the system can be found
+in manual.html and from the CUP home page mentioned below.
+
+Bug reports regarding the installation 
+process or the system as a whole should be sent to
+<cananian@alumni.princeton.edu> with "JavaCUP" in the subject.
+
+The CUP home page where the latest information regarding CUP can be found 
+(e.g., new releases) is:
+
+  http://www.cs.princeton.edu/~appel/modern/java/CUP/
+
+Enjoy,
+
+Scott Hudson
+Graphics, Visualization, and Usability Center 
+Georgia Institute of Technology
+	 
+Last updated: 23-Jul-1999 [CSA]
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diff --git a/Robust/cup/manual.html b/Robust/cup/manual.html
new file mode 100644
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+++ b/Robust/cup/manual.html
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+<html><head>
+<title>CUP User's Manual</title>
+</head>
+<body>
+
+<hr>
+<img src="cup_logo.gif" alt="[CUP Logo Image]">
+<hr>
+<h1>CUP User's Manual</h1>
+<h3><a href="http://www.cc.gatech.edu/gvu/people/Faculty/Scott.E.Hudson.html">
+Scott E. Hudson</a><br> 
+<a href="http://www.cc.gatech.edu/gvu/gvutop.html">
+Graphics Visualization and Usability Center</a><br> 
+<a href="http://www.gatech.edu/TechHome.html">
+Georgia Institute of Technology</a></h3>
+Modified by <a href="http://www.princeton.edu/~frankf">Frank
+Flannery</a>, <a href="http://www.pdos.lcs.mit.edu/~cananian/">C. Scott Ananian</a>, 
+<a href="http://www.cs.princeton.edu/~danwang">Dan Wang</a> with advice from 
+<a href="http://www.cs.princeton.edu/~appel">Andrew W. Appel</a><br>
+Last updated July 1999 (v0.10j)
+<hr>
+
+<h3>Table of Contents</h3>
+<dl compact>
+  <dt> i.  <dd> <a href="#about">About CUP Version 0.10</a>
+  <dt> 1.  <dd> <a href="#intro">Introduction and Example</a>
+  <dt> 2.  <dd> <a href="#spec">Specification Syntax</a>
+  <dt> 3.  <dd> <a href="#running">Running CUP</a>
+  <dt> 4.  <dd> <a href="#parser">Customizing the Parser</a>
+  <dt> 5.  <dd> <a href="#scanner">Scanner interface</a>
+  <dt> 6.  <dd> <a href="#errors">Error Recovery</a>
+  <dt> 7.  <dd> <a href="#conclusion">Conclusion</a>
+  <dt>     <dd> <a href="#refs">References</a>
+  <dt> A.  <dd> <a href="#appendixa">Grammar for CUP Specification Files</a>
+  <dt> B.  <dd> <a href="#appendixb">A Very Simple Example Scanner</a>
+  <dt> C.  <dd> <a href="#changes">Incompatibilites between CUP 0.9 and CUP 0.10</a>
+  <dt> D.  <dd> <a href="#bugs">Bugs</a>
+  <dt> E.  <dd> <a href="#version">Change log</a>
+</dl>
+
+<a name=about>
+<h3>i. About CUP Version 0.10</h3>
+</a> Version
+0.10 of CUP adds many new changes and features over the previous releases
+of version 0.9.  These changes attempt to make CUP more like its
+predecessor, YACC.  As a result, the old 0.9 parser specifications for CUP are
+not compatible and a reading of <a href="#changes">appendix C</a> of the new
+manual will be necessary to write new specifications.  The new version,
+however, gives the user more power and options, making parser specifications
+easier to write.
+
+<a name=intro>
+<h3>1. Introduction and Example</h3></a>
+
+This manual describes the basic operation and use of the 
+Java<a href="#trademark">(tm)</a>
+Based Constructor of Useful Parsers (CUP for short).
+CUP is a system for generating LALR parsers from simple specifications.
+It serves the same role as the widely used program YACC 
+<a href="#YACCref">[1]</a> and in fact offers most of the features of YACC.  
+However, CUP is written in Java, uses specifications including embedded 
+Java code, and produces parsers which are implemented in Java.<p>
+
+Although this manual covers all aspects of the CUP system, it is relatively
+brief, and assumes you have at least a little bit of knowledge of LR
+parsing.  A working knowledge of YACC is also very helpful in
+understanding how CUP specifications work.
+A number of compiler construction textbooks (such as 
+<a href="#dragonbook">[2</a>,<a href="#crafting">3]</a>) cover this material, 
+and discuss the YACC system (which is quite similar to this one) as a 
+specific example.  In addition, Andrew Appel's <a
+href="http://www.cs.princeton.edu/~appel/modern/java/">Modern Compiler
+Implementation in Java</a> textbook <a href="#modernjava">[4]</a> uses
+and describes CUP in the context of compiler construction.
+<p> 
+
+Using CUP involves creating a simple specification based on the
+grammar for which a parser is needed, along with construction of a
+scanner capable of breaking characters up into meaningful tokens (such
+as keywords, numbers, and special symbols).<p> 
+
+As a simple example, consider a 
+system for evaluating simple arithmetic expressions over integers.  
+This system would read expressions from standard input (each terminated 
+with a semicolon), evaluate them, and print the result on standard output.  
+A grammar for the input to such a system might look like: <pre>
+  expr_list ::= expr_list expr_part | expr_part
+  expr_part ::= expr ';'
+  expr      ::= expr '+' expr | expr '-' expr | expr '*' expr 
+	      | expr '/' expr | expr '%' expr | '(' expr ')'  
+              | '-' expr | number 
+</pre>
+To specify a parser based on this grammar, our first step is to identify and
+name the set of terminal symbols that will appear on input, and the set of 
+non-terminal symbols.  In this case, the non-terminals are: 
+
+<pre><tt>  expr_list, expr_part </tt> and <tt> expr </tt>.</pre>
+
+For terminal names we might choose:
+
+<pre><tt>  SEMI, PLUS, MINUS, TIMES, DIVIDE, MOD, NUMBER, LPAREN,</tt>
+and <tt>RPAREN</tt></pre>
+
+The experienced user will note a problem with the above grammar.  It is
+ambiguous.  An ambiguous grammar is a grammar which, given a certain
+input, can reduce the parts of the input in two different ways such as
+to give two different answers.  Take the above grammar, for
+example. given the following input: <br>
+<tt>3 + 4 * 6</tt><br>
+The grammar can either evaluate the <tt>3 + 4</tt> and then multiply
+seven by six, or it can evaluate <tt>4 * 6</tt> and then add three.
+Older versions of CUP forced the user to write unambiguous grammars, but
+now there is a construct allowing the user to specify precedences and
+associativities for terminals.  This means that the above ambiguous
+grammar can be used, after specifying precedences and associativities.
+There is more explanation later.
+
+Based on these namings we can construct a small CUP specification 
+as follows:<br>
+<hr>
+<pre><tt>// CUP specification for a simple expression evaluator (no actions)
+
+import java_cup.runtime.*;
+
+/* Preliminaries to set up and use the scanner.  */
+init with {: scanner.init();              :};
+scan with {: return scanner.next_token(); :};
+
+/* Terminals (tokens returned by the scanner). */
+terminal            SEMI, PLUS, MINUS, TIMES, DIVIDE, MOD;
+terminal            UMINUS, LPAREN, RPAREN;
+terminal Integer    NUMBER;
+
+/* Non terminals */
+non terminal            expr_list, expr_part;
+non terminal Integer    expr, term, factor;
+
+/* Precedences */
+precedence left PLUS, MINUS;
+precedence left TIMES, DIVIDE, MOD;
+precedence left UMINUS;
+
+/* The grammar */
+expr_list ::= expr_list expr_part | 
+              expr_part;
+expr_part ::= expr SEMI;
+expr      ::= expr PLUS expr 
+            | expr MINUS expr  
+            | expr TIMES expr  
+            | expr DIVIDE expr  
+            | expr MOD expr 
+	    | MINUS expr %prec UMINUS
+            | LPAREN expr RPAREN
+	    | NUMBER
+	    ;
+</tt></pre>
+<hr><br>
+We will consider each part of the specification syntax in detail later.  
+However, here we can quickly see that the specification contains four 
+main parts.  The first part provides preliminary and miscellaneous declarations
+to specify how the parser is to be generated, and supply parts of the 
+runtime code.  In this case we indicate that the <tt>java_cup.runtime</tt>
+classes should be imported, then supply a small bit of initialization code,
+and some code for invoking the scanner to retrieve the next input token.
+The second part of the specification declares terminals and non-terminals,
+and associates object classes with each.  In this case, the terminals
+are declared as either with no type, or of type
+<tt>Integer</tt>.  The specified type of the
+terminal or non-terminal is the type of the value of those terminals or
+non-terminals.  If no type is specified, the terminal or non-terminal
+carries no value.  Here, no type indicates that these
+terminals and non-terminals hold no value.  
+The third part specifies the precedence and
+associativity of terminals.  The last precedence declaration give its
+terminals the highest precedence. The final 
+part of the specification contains the grammar.<p>
+
+ 
+To produce a parser from this specification we use the CUP generator.
+If this specification were stored in a file <tt>parser.cup</tt>, then 
+(on a Unix system at least) we might invoke CUP using a command like:
+<pre><tt> java java_cup.Main &lt; parser.cup</tt> </pre>
+or (starting with CUP 0.10k):
+<pre><tt> java java_cup.Main parser.cup</tt> </pre>
+The system will produce two Java source files containing 
+parts of the generated parser: <tt>sym.java</tt> and <tt>parser.java</tt>
+(these names can be changed with command-line options; see 
+<A HREF="#running">below</a>).  
+As you might expect, these two files contain declarations for the classes 
+<tt>sym</tt> and <tt>parser</tt>. The <tt>sym</tt> class contains a series of 
+constant declarations, one for each terminal symbol.  This is typically used 
+by the scanner to refer to symbols (e.g. with code such as 
+"<tt>return new Symbol(sym.SEMI);</tt>" ).  The <tt>parser</tt> class 
+implements the parser itself.<p>
+
+The specification above, while constructing a full parser, does not perform 
+any semantic actions &emdash; it will only indicate success or failure of a parse.
+To calculate and print values of each expression, we must embed Java
+code within the parser to carry out actions at various points.  In CUP,
+actions are contained in <i>code strings</i> which are surrounded by delimiters 
+of the form <tt>{:</tt> and <tt>:}</tt> (we can see examples of this in the 
+<tt>init with</tt> and <tt>scan with</tt> clauses above).  In general, the 
+system records all characters within the delimiters, but does not try to check 
+that it contains valid Java code.<p>
+
+A more complete CUP specification for our example system (with actions 
+embedded at various points in the grammar) is shown below:<br>
+<hr>
+<pre><tt>// CUP specification for a simple expression evaluator (w/ actions)
+
+import java_cup.runtime.*;
+
+/* Preliminaries to set up and use the scanner.  */
+init with {: scanner.init();              :};
+scan with {: return scanner.next_token(); :};
+
+/* Terminals (tokens returned by the scanner). */
+terminal           SEMI, PLUS, MINUS, TIMES, DIVIDE, MOD;
+terminal           UMINUS, LPAREN, RPAREN;
+terminal Integer   NUMBER;
+
+/* Non-terminals */
+non terminal            expr_list, expr_part;
+non terminal Integer    expr;
+
+/* Precedences */
+precedence left PLUS, MINUS;
+precedence left TIMES, DIVIDE, MOD;
+precedence left UMINUS;
+
+/* The grammar */
+expr_list ::= expr_list expr_part 
+	      | 
+              expr_part;
+
+expr_part ::= expr:e 
+	      {: System.out.println("= " + e); :} 
+              SEMI              
+	      ;
+
+expr      ::= expr:e1 PLUS expr:e2    
+	      {: RESULT = new Integer(e1.intValue() + e2.intValue()); :} 
+	      | 
+              expr:e1 MINUS expr:e2    
+              {: RESULT = new Integer(e1.intValue() - e2.intValue()); :} 
+	      | 
+              expr:e1 TIMES expr:e2 
+	      {: RESULT = new Integer(e1.intValue() * e2.intValue()); :} 
+	      | 
+              expr:e1 DIVIDE expr:e2 
+	      {: RESULT = new Integer(e1.intValue() / e2.intValue()); :} 
+	      | 
+              expr:e1 MOD expr:e2 
+	      {: RESULT = new Integer(e1.intValue() % e2.intValue()); :} 
+	      | 
+              NUMBER:n                 
+	      {: RESULT = n; :} 
+	      | 
+              MINUS expr:e             
+	      {: RESULT = new Integer(0 - e.intValue()); :} 
+	      %prec UMINUS
+	      | 
+              LPAREN expr:e RPAREN     
+	      {: RESULT = e; :} 
+	      ;
+</tt></pre>
+<hr><br>
+Here we can see several changes.  Most importantly, code to be executed at 
+various points in the parse is included inside code strings delimited by 
+<tt>{:</tt> and <tt>:}</tt>.  In addition, labels have been placed on various 
+symbols in the right hand side of productions.  For example in:<br>
+<pre>  expr:e1 PLUS expr:e2    
+	{: RESULT = new Integer(e1.intValue() + e2.intValue()); :} 
+</pre>
+<a name="RES_part">
+the first non-terminal <tt>expr</tt> has been labeled with <tt>e1</tt>, and 
+the second with <tt>e2</tt>.  The left hand side value 
+of each production is always implicitly labeled as <tt>RESULT</tt>.<p>
+
+Each symbol appearing in a production is represented at runtime by an
+object of type <tt>Symbol</tt> on the parse stack.  The labels refer to
+the instance variable <tt>value</tt> in those objects.  In the
+expression <tt>expr:e1 PLUS expr:e2</tt>, <tt>e1</tt> and <tt>e2</tt>
+refer to objects of type Integer.  These objects are in the value fields
+of the objects of type <tt>Symbol</tt> representing those non-terminals
+on the parse stack.  <tt>RESULT</tt> is of type <tt>Integer</tt> as
+well, since the resulting non-terminal <tt>expr</tt> was declared as of 
+type <tt>Integer</tt>.  This object becomes the <tt>value</tt> instance
+variable of a new <tt>Symbol</tt> object.<p>  
+
+For each label, two more variables accessible to the user are declared.
+A left and right value labels are passed to the code string, so that the
+user can find out where the left and right side of each terminal or
+non-terminal is in the input stream.  The name of these variables is the
+label name, plus <tt>left</tt> or <tt>right</tt>.  for example, given
+the right hand side of a production <tt>expr:e1 PLUS expr:e2</tt> the
+user could not only access variables <tt>e1</tt> and <tt>e2</tt>, but
+also <tt>e1left, e1right, e2left</tt> and <tt>e2right</tt>.  these
+variables are of type <tt>int</tt>.<p>    
+
+<a name="lex_part">
+
+The final step in creating a working parser is to create a <i>scanner</i> (also
+known as a <i>lexical analyzer</i> or simply a <i>lexer</i>).  This routine is 
+responsible for reading individual characters, removing things things like
+white space and comments, recognizing which terminal symbols from the 
+grammar each group of characters represents, then returning Symbol objects
+representing these symbols to the parser.
+The terminals will be retrieved with a call to the
+scanner function.  In the example, the parser will call
+<tt>scanner.next_token()</tt>. The scanner should return objects of
+type <tt>java_cup.runtime.Symbol</tt>.  This type is very different than
+older versions of CUP's <tt>java_cup.runtime.symbol</tt>.  These Symbol
+objects contains the instance variable <tt>value</tt> of type Object, 
+which should be
+set by the lexer.  This variable refers to the value of that symbol, and
+the type of object in value should be of the same type as declared in
+the <tt>terminal</tt> and <tt>non terminal</tt> declarations.  In the
+above example, if the lexer wished to pass a NUMBER token, it should
+create a <tt>Symbol</tt> with the <tt>value</tt> instance variable
+filled with an object of type <tt>Integer</tt>.  <code>Symbol</code>
+objects corresponding to terminals and non-terminals with no value
+have a null value field.<p>
+
+The code contained in the <tt>init with</tt> clause of the specification 
+will be executed before any tokens are requested.  Each token will be 
+requested using whatever code is found in the <tt>scan with</tt> clause.
+Beyond this, the exact form the scanner takes is up to you; however
+note that each call to the scanner function should return a new
+instance of <code>java_cup.runtime.Symbol</code> (or a subclass).
+These symbol objects are annotated with parser information and pushed
+onto a stack; reusing objects will result in the parser annotations
+being scrambled.  As of CUP 0.10j, <code>Symbol</code> reuse should be
+detected if it occurs; the parser will throw an <code>Error</code>
+telling you to fix your scanner.<p>
+
+In the <a href="#spec">next section</a> a more detailed and formal 
+explanation of all parts of a CUP specification will be given.  
+<a href="#running">Section 3</a> describes options for running the 
+CUP system.  <a href="#parser">Section 4</a> discusses the details 
+of how to customize a CUP parser, while <a href="#scanner">section 5</a>
+discusses the scanner interface added in CUP 0.10j. <a href="#errors">Section
+ 6</a> considers error recovery.  Finally, <a href="#conclusion">Section 7</a> 
+provides a conclusion.
+
+<a name="spec">
+<h3>2. Specification Syntax</h3></a>
+Now that we have seen a small example, we present a complete description of all 
+parts of a CUP specification.  A specification has four sections with 
+a total of eight specific parts (however, most of these are optional).  
+A specification consists of:
+<ul>
+<li> <a href="#package_spec">package and import specifications</a>,
+<li> <a href="#code_part">user code components</a>,
+<li> <a href="#symbol_list">symbol (terminal and non-terminal) lists</a>, 
+<li> <a href="#precedence">precedence declarations</a>, and
+<li> <a href="#production_list">the grammar</a>.
+</ul>
+Each of these parts must appear in the order presented here.  (A complete 
+grammar for the specification language is given in 
+<a href="#appendixa">Appendix A</a>.)  The particulars of each part of
+the specification are described in the subsections below.<p>
+
+<h5><a name="package_spec">Package and Import Specifications</a></h5>
+
+A specification begins with optional <tt>package</tt> and <tt>import</tt> 
+declarations.  These have the same syntax, and play the same 
+role, as the package and import declarations found in a normal Java program.
+A package declaration is of the form:
+
+<pre><tt>    package <i>name</i>;</tt></pre>
+
+where name <tt><i>name</i></tt> is a Java package identifier, possibly in
+several parts separated by ".".  In general, CUP employs Java lexical
+conventions.  So for example, both styles of Java comments are supported,
+and identifiers are constructed beginning with a letter, dollar
+sign ($), or underscore (_), which can then be followed by zero or more
+letters, numbers, dollar signs, and underscores.<p>
+
+After an optional <tt>package</tt> declaration, there can be zero or more 
+<tt>import</tt> declarations. As in a Java program these have the form:
+
+<pre><tt>    import <i>package_name.class_name</i>;</tt>
+</pre>
+or
+<pre><tt>    import <i>package_name</i>.*;</tt>
+</pre>
+
+The package declaration indicates what package the <tt>sym</tt> and 
+<tt>parser</tt> classes that are generated by the system will be in.  
+Any import declarations that appear in the specification will also appear
+in the source file for the <tt>parser</tt> class allowing various names from
+that package to be used directly in user supplied action code.
+
+<h5><a name="code_part">User Code Components</a></h5>
+
+Following the optional <tt>package</tt> and <tt>import</tt> declarations
+are a series of optional declarations that allow user code to be included
+as part of the generated parser (see <a href="#parser">Section 4</a> for a 
+full description of how the parser uses this code).  As a part of the parser 
+file, a separate non-public class to contain all embedded user actions is 
+produced.  The first <tt>action code</tt> declaration section allows code to 
+be included in this class.  Routines and variables for use by the code 
+embedded in the grammar would normally be placed in this section (a typical 
+example might be symbol table manipulation routines).  This declaration takes 
+the form:
+
+<pre><tt>    action code {: ... :};</tt>
+</pre>
+
+where <tt>{: ... :}</tt> is a code string whose contents will be placed
+directly within the <tt>action class</tt> class declaration.<p>
+
+After the <tt>action code</tt> declaration is an optional 
+<tt>parser code</tt> declaration.  This declaration allows methods and
+variable to be placed directly within the generated parser class.
+Although this is less common, it can be helpful when customizing the 
+parser &emdash; it is possible for example, to include scanning methods inside
+the parser and/or override the default error reporting routines.  This 
+declaration is very similar to the <tt>action code</tt> declaration and 
+takes the form:
+
+<pre><tt>    parser code {: ... :};</tt>
+</pre>
+
+Again, code from the code string is placed directly into the generated parser
+class definition.<p>
+
+Next in the specification is the optional <tt>init</tt> declaration 
+which has the form:
+
+<pre><tt>    init with {: ... :};</tt></pre>
+
+This declaration provides code that will be executed by the parser
+before it asks for the first token.  Typically, this is used to initialize
+the scanner as well as various tables and other data structures that might
+be needed by semantic actions.  In this case, the code given in the code
+string forms the body of a <tt>void</tt> method inside the <tt>parser</tt> 
+class.<p>
+
+The final (optional) user code section of the specification indicates how 
+the parser should ask for the next token from the scanner.  This has the
+form:
+
+<pre><tt>    scan with {: ... :};</tt></pre>
+
+As with the <tt>init</tt> clause, the contents of the code string forms
+the body of a method in the generated parser.  However, in this case
+the method returns an object of type <tt>java_cup.runtime.Symbol</tt>.
+Consequently the code found in the <tt>scan with</tt> clause should 
+return such a value.  See <a href="#scanner">section 5</a> for
+information on the default behavior if the <code>scan with</code>
+section is omitted.<p>
+
+As of CUP 0.10j the action code, parser code, init code, and scan with
+sections may appear in any order. They must, however, precede the
+symbol lists.<p>
+
+<h5><a name="symbol_list">Symbol Lists</a></h5>
+
+Following user supplied code comes the first required part of the 
+specification: the symbol lists.  These declarations are responsible 
+for naming and supplying a type for each terminal and non-terminal
+symbol that appears in the grammar.  As indicated above, each terminal
+and non-terminal symbol is represented at runtime with a <tt>Symbol</tt>
+object.  In
+the case of terminals, these are returned by the scanner and placed on
+the parse stack.  The lexer should put the value of the terminal in the
+<tt>value</tt> instance variable.  
+In the case of non-terminals these replace a series
+of <tt>Symbol</tt> objects on the parse stack whenever the right hand side of
+some production is recognized.  In order to tell the parser which object
+types should be used for which symbol, <tt>terminal</tt> and 
+<tt>non terminal</tt> declarations are used.  These take the forms:
+
+<pre><tt>    terminal <i>classname</i> <i>name1, name2,</i> ...;</tt>
+<tt>    non terminal <i>classname</i> <i>name1, name2,</i> ...;</tt>
+<tt>    terminal <i>name1, name2,</i> ...;</tt>
+</pre>
+
+and
+
+<pre><tt>    non terminal <i>name1, name2,</i> ...;</tt>
+</pre>
+
+where <tt><i>classname</i></tt> can be a multiple part name separated with
+"."s.  The
+<tt><i>classname</i></tt> specified represents the type of the value of
+that terminal or non-terminal.  When accessing these values through
+labels, the users uses the type declared. the <tt><i>classname</i></tt>
+can be of any type.  If no <tt><i>classname</i></tt> is given, then the
+terminal or non-terminal holds no value.  a label referring to such a
+symbol with have a null value. As of CUP 0.10j, you may specify
+non-terminals the declaration "<code>nonterminal</code>" (note, no
+space) as well as the original "<code>non terminal</code>" spelling.<p>
+
+Names of terminals and non-terminals cannot be CUP reserved words;
+these include "code", "action", "parser", "terminal", "non",
+"nonterminal", "init", "scan", "with", "start", "precedence", "left",
+"right", "nonassoc", "import", and "package".<p>
+
+<h5><a name="precedence">Precedence and Associativity declarations</a></h5>
+
+The third section, which is optional, specifies the precedences and
+associativity of terminals.  This is useful for parsing with ambiguous
+grammars, as done in the example above. There are three type of
+precedence/associativity declarations:
+<pre><tt>
+	precedence left     <i>terminal</i>[, <i>terminal</i>...];
+	precedence right    <i>terminal</i>[, <i>terminal</i>...];
+	precedence nonassoc <i>terminal</i>[, <i>terminal</i>...];
+</tt></pre>
+
+The comma separated list indicates that those terminals should have the
+associativity specified at that precedence level and the precedence of
+that declaration.  The order of precedence, from highest to lowest, is
+bottom to top.  Hence, this declares that multiplication and division have
+higher precedence than addition and subtraction:
+<pre><tt>
+	precedence left  ADD, SUBTRACT;
+	precedence left  TIMES, DIVIDE;
+</tt></pre>
+Precedence resolves shift reduce problems.  For example, given the input
+to the above example parser <tt>3 + 4 * 8</tt>, the parser doesn't know
+whether to reduce <tt>3 + 4</tt> or shift the '*' onto the stack.
+However, since '*' has a higher precedence than '+', it will be shifted
+and the multiplication will be performed before the addition.<p>
+
+CUP assigns each one of its terminals a precedence according to these
+declarations.  Any terminals not in this declaration have lowest
+precedence.  CUP also assigns each of its productions a precedence.
+That precedence is equal to the precedence of the last terminal in that
+production.  If the production has no terminals, then it has lowest
+precedence. For example, <tt>expr ::= expr TIMES expr</tt> would have
+the same precedence as <tt>TIMES</tt>.  When there is a shift/reduce
+conflict, the parser determines whether the terminal to be shifted has a
+higher precedence, or if the production to reduce by does.  If the
+terminal has higher precedence, it it shifted, if the production has
+higher precedence, a reduce is performed.  If they have equal
+precedence, associativity of the terminal determine what happens.<p>
+
+An associativity is assigned to each terminal used in the
+precedence/associativity declarations.  The three associativities are
+<tt>left, right</tt> and <tt>nonassoc</tt>  Associativities are also
+used to resolve shift/reduce conflicts, but only in the case of equal
+precedences.  If the associativity of the terminal that can be shifted
+is <tt>left</tt>, then a reduce is performed.  This means, if the input
+is a string of additions, like <tt>3 + 4 + 5 + 6 + 7</tt>, the parser
+will <i>always</i> reduce them from left to right, in this case,
+starting with <tt>3 + 4</tt>.  If the associativity of the terminal is
+<tt>right</tt>, it is shifted onto the stack.  hence, the reductions
+will take place from right to left.  So, if PLUS were declared with
+associativity of <tt>right</tt>, the <tt>6 + 7</tt> would be reduced
+first in the above string.  If a terminal is declared as
+<tt>nonassoc</tt>, then two consecutive occurrences of equal precedence
+non-associative terminals generates an error.  This is useful for
+comparison operations.  For example, if the input string is 
+<tt>6 == 7 == 8 == 9</tt>, the parser should generate an error.  If '=='
+is declared as <tt>nonassoc</tt> then an error will be generated. <p>
+
+All terminals not used in the precedence/associativity declarations are
+treated as lowest precedence.  If a shift/reduce error results,
+involving two such terminals, it cannot be resolved, as the above
+conflicts are, so it will be reported.<p>
+
+<h5><a name="production_list">The Grammar</a></h5>
+
+The final section of a CUP declaration provides the grammar.  This 
+section optionally starts with a declaration of the form:
+
+<pre><tt>    start with <i>non-terminal</i>;</tt>
+</pre>
+
+This indicates which non-terminal is the <i>start</i> or <i>goal</i> 
+non-terminal for parsing.  If a start non-terminal is not explicitly
+declared, then the non-terminal on the left hand side of the first 
+production will be used.  At the end of a successful parse, CUP returns
+an object of type <tt>java_cup.runtime.Symbol</tt>.  This
+<tt>Symbol</tt>'s value instance variable contains the final reduction
+result.<p>
+
+The grammar itself follows the optional <tt>start</tt> declaration.  Each
+production in the grammar has a left hand side non-terminal followed by 
+the symbol "<tt>::=</tt>", which is then followed by a series of zero or more
+actions, terminal, or non-terminal
+symbols, followed by an optional contextual precedence assignment, 
+and terminated with a semicolon (;).<p>
+
+<a name="label_part">
+
+Each symbol on the right hand side can optionally be labeled with a name.
+Label names appear after the symbol name separated by a colon (:).  Label
+names must be unique within the production, and can be used within action
+code to refer to the value of the symbol.  Along with the label, two
+more variables are created, which are the label plus <tt>left</tt> and
+the label plus <tt>right</tt>.  These are <tt>int</tt> values that
+contain the right and left locations of what the terminal or
+non-terminal covers in the input file.  These values must be properly
+initialized in the terminals by the lexer. The left and right values
+then propagate to non-terminals to which productions reduce.<p>
+ 
+If there are several productions for the same non-terminal they may be 
+declared together.  In this case the productions start with the non-terminal 
+and "<tt>::=</tt>".  This is followed by multiple right hand sides each 
+separated by a bar (|).  The full set of productions is then terminated by a 
+semicolon.<p>
+
+Actions appear in the right hand side as code strings (e.g., Java code inside
+<tt>{:</tt> ... <tt>:}</tt> delimiters).  These are executed by the parser
+at the point when the portion of the production to the left of the 
+action has been recognized.  (Note that the scanner will have returned the 
+token one past the point of the action since the parser needs this extra
+<i>lookahead</i> token for recognition.)<p>
+
+<a name="cpp">
+
+Contextual precedence assignments follow all the symbols and actions of
+the right hand side of the production whose precedence it is assigning.
+Contextual precedence assignment allows a production to be assigned a
+precedence not based on the last terminal in it.  A good example is
+shown in the above sample parser specification:
+
+<pre><tt>
+	precedence left PLUS, MINUS;
+	precedence left TIMES, DIVIDE, MOD;
+	precedence left UMINUS;
+
+	expr ::=  MINUS expr:e             
+	          {: RESULT = new Integer(0 - e.intValue()); :} 
+	          %prec UMINUS
+</tt></pre>
+
+Here, there production is declared as having the precedence of UMINUS.
+Hence, the parser can give the MINUS sign two different precedences,
+depending on whether it is a unary minus or a subtraction operation. 
+
+<a name="running">
+<h3>3. Running CUP</h3></a>
+
+As mentioned above, CUP is written in Java.  To invoke it, one needs
+to use the Java interpreter to invoke the static method 
+<tt>java_cup.Main()</tt>, passing an array of strings containing options.  
+Assuming a Unix machine, the simplest way to do this is typically to invoke it 
+directly from the command line with a command such as: 
+
+<pre><tt>    java java_cup.Main <i>options</i> &lt; <i>inputfile</i></tt></pre>
+
+Once running, CUP expects to find a specification file on standard input
+and produces two Java source files as output. Starting with CUP 0.10k,
+the final command-line argument may be a filename, in which case the
+specification will be read from that file instead of from standard input.<p>
+
+In addition to the specification file, CUP's behavior can also be changed
+by passing various options to it.  Legal options are documented in
+<code>Main.java</code> and include:
+<dl>
+  <dt><tt>-package</tt> <i>name</i>  
+  <dd>Specify that the <tt>parser</tt> and <tt>sym</tt> classes are to be 
+       placed in the named package.  By default, no package specification 
+       is put in the generated code (hence the classes default to the special 
+       "unnamed" package).
+
+  <dt><tt>-parser</tt> <i>name</i>   
+  <dd>Output parser and action code into a file (and class) with the given
+      name instead of the default of "<tt>parser</tt>".
+
+  <dt><tt>-symbols</tt> <i>name</i>  
+  <dd>Output the symbol constant code into a class with the given
+      name instead of the default of "<tt>sym</tt>".
+
+  <dt><tt>-interface</tt>
+  <dd>Outputs the symbol constant code as an <code>interface</code>
+      rather than as a <code>class</code>.
+
+  <dt><tt>-nonterms</tt>      
+  <dd>Place constants for non-terminals into the  symbol constant class.
+      The parser does not need these symbol constants, so they are not normally
+      output.  However, it can be very helpful to refer to these constants
+      when debugging a generated parser.
+
+  <dt><tt>-expect</tt> <i>number</i>      
+  <dd>During parser construction the system may detect that an ambiguous 
+      situation would occur at runtime.  This is called a <i>conflict</i>.  
+      In general, the parser may be unable to decide whether to <i>shift</i> 
+      (read another symbol) or <i>reduce</i> (replace the recognized right 
+      hand side of a production with its left hand side).  This is called a 
+      <i>shift/reduce conflict</i>.  Similarly, the parser may not be able 
+      to decide between reduction with two different productions.  This is 
+      called a <i>reduce/reduce conflict</i>.  Normally, if one or more of 
+      these conflicts occur, parser generation is aborted.  However, in 
+      certain carefully considered cases it may be advantageous to 
+      arbitrarily break such a conflict.  In this case CUP uses YACC 
+      convention and resolves shift/reduce conflicts by shifting, and 
+      reduce/reduce conflicts using the "highest priority" production (the 
+      one declared first in the specification).  In order to enable automatic 
+      breaking of conflicts the <tt>-expect</tt> option must be given 
+      indicating exactly how many conflicts are expected.  Conflicts
+      resolved by precedences and associativities are not reported.
+
+  <dt><tt>-compact_red</tt>   
+  <dd>Including this option enables a table compaction optimization involving
+      reductions.  In particular, it allows the most common reduce entry in 
+      each row of the parse action table to be used as the default for that 
+      row.  This typically saves considerable room in the tables, which can 
+      grow to be very large.  This optimization has the effect of replacing 
+      all error entries in a row with the default reduce entry.  While this 
+      may sound dangerous, if not down right incorrect, it turns out that this 
+      does not affect the correctness of the parser.  In particular, some
+      changes of this type are inherent in LALR parsers (when compared to 
+      canonical LR parsers), and the resulting parsers will still never 
+      read past the first token at which the error could be detected.
+      The parser can, however, make extra erroneous reduces before detecting
+      the error, so this can degrade the parser's ability to do 
+      <a href="#errors">error recovery</a>.
+      (Refer to reference [2] pp. 244-247 or reference [3] pp. 190-194 for a 
+      complete explanation of this compaction technique.) <br><br>
+
+      This option is typically used to work-around the java bytecode
+      limitations on table initialization code sizes.  However, CUP
+      0.10h introduced a string-encoding for the parser tables which
+      is not subject to the standard method-size limitations.
+      Consequently, use of this option should no longer be required
+      for large grammars.
+
+  <dt><tt>-nowarn</tt>        
+  <dd>This options causes all warning messages (as opposed to error messages)
+      produced by the system to be suppressed.
+
+  <dt><tt>-nosummary</tt>     
+  <dd>Normally, the system prints a summary listing such things as the 
+      number of terminals, non-terminals, parse states, etc. at the end of
+      its run.  This option suppresses that summary.
+
+  <dt><tt>-progress</tt>      
+  <dd>This option causes the system to print short messages indicating its
+      progress through various parts of the parser generation process.
+
+  <dt><tt>-dump_grammar</tt>  
+  <dt><tt>-dump_states</tt>   
+  <dt><tt>-dump_tables</tt>   
+  <dt><tt>-dump</tt>          
+  <dd> These options cause the system to produce a human readable dump of
+       the grammar, the constructed parse states (often needed to resolve
+       parse conflicts), and the parse tables (rarely needed), respectively.
+       The <tt>-dump</tt> option can be used to produce all of these dumps.
+
+  <dt><tt>-time</tt>          
+  <dd>This option adds detailed timing statistics to the normal summary of
+      results.  This is normally of great interest only to maintainers of 
+      the system itself.
+
+  <dt><tt>-debug</tt>          
+  <dd>This option produces voluminous internal debugging information about
+      the system as it runs.  This is normally of interest only to maintainers 
+      of the system itself.
+
+  <dt><tt>-nopositions</tt>          
+  <dd>This option keeps CUP from generating code to propagate the left
+      and right hand values of terminals to non-terminals, and then from
+      non-terminals to other terminals.  If the left and right values aren't
+      going to be used by the parser, then it will save some runtime
+      computation to not generate these position propagations.  This option
+      also keeps the left and right label variables from being generated, so
+      any reference to these will cause an error.
+
+  <dt><tt>-noscanner</tt>
+  <dd>CUP 0.10j introduced <a href="#scanner">improved scanner
+  integration</a> and a new interface,
+  <code>java_cup.runtime.Scanner</code>.  By default, the 
+  generated parser refers to this interface, which means you cannot
+  use these parsers with CUP runtimes older than 0.10j.  If your
+  parser does not use the new scanner integration features, then you
+  may specify the <code>-noscanner</code> option to suppress the
+  <code>java_cup.runtime.Scanner</code> references and allow
+  compatibility with old runtimes.  Not many people should have reason
+  to do this.
+
+  <dt><tt>-version</tt>
+  <dd>Invoking CUP with the <code>-version</code> flag will cause it
+  to print out the working version of CUP and halt.  This allows
+  automated CUP version checking for Makefiles, install scripts and
+  other applications which may require it.
+</dl>
+
+<a name="parser">
+<h3>4. Customizing the Parser</h3></a>
+
+Each generated parser consists of three generated classes.  The 
+<tt>sym</tt> class (which can be renamed using the <tt>-symbols</tt>
+option) simply contains a series of <tt>int</tt> constants,
+one for each terminal.  Non-terminals are also included if the <tt>-nonterms</tt>
+option is given.  The source file for the <tt>parser</tt> class (which can
+be renamed using the <tt>-parser</tt> option) actually contains two 
+class definitions, the public <tt>parser</tt> class that implements the 
+actual parser, and another non-public class (called <tt>CUP$action</tt>) which 
+encapsulates all user actions contained in the grammar, as well as code from 
+the <tt>action code</tt> declaration.  In addition to user supplied code, this
+class contains one method: <tt>CUP$do_action</tt> which consists of a large 
+switch statement for selecting and executing various fragments of user 
+supplied action code.  In general, all names beginning with the prefix of 
+<tt>CUP$</tt> are reserved for internal uses by CUP generated code. <p> 
+
+The <tt>parser</tt> class contains the actual generated parser.  It is 
+a subclass of <tt>java_cup.runtime.lr_parser</tt> which implements a 
+general table driven framework for an LR parser.  The generated <tt>parser</tt>
+class provides a series of tables for use by the general framework.  
+Three tables are provided:
+<dl compact>
+<dt>the production table 
+<dd>provides the symbol number of the left hand side non-terminal, along with
+    the length of the right hand side, for each production in the grammar,
+<dt>the action table
+<dd>indicates what action (shift, reduce, or error) is to be taken on each 
+    lookahead symbol when encountered in each state, and
+<dt>the reduce-goto table
+<dd>indicates which state to shift to after reduces (under each non-terminal
+from each state). 
+</dl>
+(Note that the action and reduce-goto tables are not stored as simple arrays,
+but use a compacted "list" structure to save a significant amount of space.
+See comments the runtime system source code for details.)<p>
+
+Beyond the parse tables, generated (or inherited) code provides a series 
+of methods that can be used to customize the generated parser.  Some of these
+methods are supplied by code found in part of the specification and can 
+be customized directly in that fashion.  The others are provided by the
+<tt>lr_parser</tt> base class and can be overridden with new versions (via
+the <tt>parser code</tt> declaration) to customize the system.  Methods
+available for customization include:
+<dl compact>
+<dt><tt>public void user_init()</tt>
+<dd>This method is called by the parser prior to asking for the first token 
+    from the scanner.  The body of this method contains the code from the 
+    <tt>init with</tt> clause of the the specification.  
+<dt><a name="scan_method"><tt>public java_cup.runtime.Symbol scan()</tt></a>
+<dd>This method encapsulates the scanner and is called each time a new
+    terminal is needed by the parser.  The body of this method is 
+    supplied by the <tt>scan with</tt> clause of the specification, if
+    present; otherwise it returns <code>getScanner().next_token()</code>.
+<dt><tt>public java_cup.runtime.Scanner getScanner()</tt>
+<dd>Returns the default scanner.  See <a href="#scanner">section 5</a>.
+<dt><tt>public void setScanner(java_cup.runtime.Scanner s)</tt>
+<dd>Sets the default scanner.  See <a href="#scanner">section 5</a>.
+<dt><tt> public void report_error(String message, Object info)</tt>
+<dd>This method should be called whenever an error message is to be issued.  In
+    the default implementation of this method, the first parameter provides 
+    the text of a message which is printed on <tt>System.err</tt> 
+    and the second parameter is simply ignored.  It is very typical to
+    override this method in order to provide a more sophisticated error
+    reporting mechanism.
+<dt><tt>public void report_fatal_error(String message, Object info)</tt>
+<dd>This method should be called whenever a non-recoverable error occurs.  It 
+    responds by calling <tt>report_error()</tt>, then aborts parsing
+    by calling the parser method <tt>done_parsing()</tt>, and finally
+    throws an exception.  (In general <tt>done_parsing()</tt> should be called 
+    at any point that parsing needs to be terminated early).
+<dt><tt>public void syntax_error(Symbol cur_token)</tt>
+<dd>This method is called by the parser as soon as a syntax error is detected
+    (but before error recovery is attempted).  In the default implementation it
+    calls: <tt>report_error("Syntax error", null);</tt>.
+<dt><tt>public void unrecovered_syntax_error(Symbol cur_token)</tt>
+<dd>This method is called by the parser if it is unable to recover from a 
+    syntax error.  In the default implementation it calls:
+    <tt>report_fatal_error("Couldn't repair and continue parse", null);</tt>.
+<dt><tt> protected int error_sync_size()</tt>
+<dd>This method is called by the parser to determine how many tokens it must
+    successfully parse in order to consider an error recovery successful.
+    The default implementation returns 3.  Values below 2 are not recommended.
+    See the section on <a href="#errors">error recovery</a> for details.
+</dl>
+
+Parsing itself is performed by the method <tt>public Symbol parse()</tt>.  
+This method starts by getting references to each of the parse tables, 
+then initializes a <tt>CUP$action</tt> object (by calling 
+<tt>protected void init_actions()</tt>). Next it calls <tt>user_init()</tt>,
+then fetches the first lookahead token with a call to <tt>scan()</tt>.
+Finally, it begins parsing.  Parsing continues until <tt>done_parsing()</tt>
+is called (this is done automatically, for example, when the parser
+accepts).  It then returns a <tt>Symbol</tt> with the <tt>value</tt>
+instance variable containing the RESULT of the start production, or
+<tt>null</tt>, if there is no value.<p>
+
+In addition to the normal parser, the runtime system also provides a debugging
+version of the parser.  This operates in exactly the same way as the normal
+parser, but prints debugging messages (by calling 
+<tt>public void debug_message(String mess)</tt> whose default implementation
+prints a message to <tt>System.err</tt>).<p>
+
+Based on these routines, invocation of a CUP parser is typically done
+with code such as:
+<pre>
+      /* create a parsing object */
+      parser parser_obj = new parser();
+
+      /* open input files, etc. here */
+      Symbol parse_tree = null;
+
+      try {
+        if (do_debug_parse)
+          parse_tree = parser_obj.debug_parse();
+        else
+          parse_tree = parser_obj.parse();
+      } catch (Exception e) {
+        /* do cleanup here - - possibly rethrow e */
+      } finally {
+	/* do close out here */
+      }
+</pre>
+
+<a name="scanner">
+<h3>5. Scanner Interface</h3></a>
+
+In CUP 0.10j scanner integration was improved according to
+suggestions made by <a href="http://www.smartsc.com">David MacMahon</a>.
+The changes make it easier to incorporate JLex and other
+automatically-generated scanners into CUP parsers.<p>
+
+To use the new code, your scanner should implement the
+<code>java_cup.runtime.Scanner</code> interface, defined as:
+<pre>
+package java_cup.runtime;
+
+public interface Scanner {
+    public Symbol next_token() throws java.lang.Exception;
+}
+</pre><p>
+
+In addition to the methods described in <a href="#parser">section
+4</a>, the <code>java_cup.runtime.lr_parser</code> class has two new
+accessor methods, <code>setScanner()</code> and <code>getScanner()</code>.
+The default implementation of <a href="#scan_method"><code>scan()</code></a>
+is:
+<pre>
+  public Symbol scan() throws java.lang.Exception {
+    Symbol sym = getScanner().next_token();
+    return (sym!=null) ? sym : new Symbol(EOF_sym());
+  }
+</pre><p>
+The generated parser also contains a constructor which takes a
+<code>Scanner</code> and calls <code>setScanner()</code> with it. In
+most cases, then, the <code>init with</code> and <code>scan
+with</code> directives may be omitted.  You can simply create the
+parser with a reference to the desired scanner:
+<pre>
+      /* create a parsing object */
+      parser parser_obj = new parser(new my_scanner());
+</pre>
+or set the scanner after the parser is created:
+<pre>
+      /* create a parsing object */
+      parser parser_obj = new parser();
+      /* set the default scanner */
+      parser_obj.setScanner(new my_scanner());
+</pre><p>
+Note that because the parser uses look-ahead, resetting the scanner in
+the middle of a parse is not recommended. If you attempt to use the
+default implementation of <code>scan()</code> without first calling
+<code>setScanner()</code>, a <code>NullPointerException</code> will be
+thrown.<p>
+As an example of scanner integration, the following three lines in the
+lexer-generator input are all that is required to use a 
+<a href="http://www.cs.princeton.edu/~appel/modern/java/JLex/">JLex</a>
+or <a href="http://www.jflex.de/">JFlex</A>
+scanner with CUP:
+<pre>
+%implements java_cup.runtime.Scanner
+%function next_token
+%type java_cup.runtime.Symbol
+</pre>
+The JLex directive <code>%cup</code>
+abbreviates the above three directive in JLex versions 1.2.5 and above.
+Invoking the parser with the JLex scanner is then simply:
+<pre>
+parser parser_obj = new parser( new Yylex( some_InputStream_or_Reader));
+</pre><p>
+
+Note CUP handles the JLex/JFlex convention of returning null on EOF
+without a problem, so an <code>%eofval</code> directive is not
+required in the JLex specification (this feature was added in CUP 0.10k).
+
+The simple_calc example in the CUP distribution illustrates the use of
+the scanner integration features with a hand-coded scanner.
+The CUP website has a minimal CUP/JLex integration example for study.<p>
+
+<a name="errors">
+<h3>6. Error Recovery</h3></a>
+
+A final important aspect of building parsers with CUP is 
+support for syntactic error recovery.  CUP uses the same 
+error recovery mechanisms as YACC.  In particular, it supports
+a special error symbol (denoted simply as <tt>error</tt>).
+This symbol plays the role of a special non-terminal which, instead of
+being defined by productions, instead matches an erroneous input 
+sequence.<p>
+
+The error symbol only comes into play if a syntax error is
+detected.  If a syntax error is detected then the parser tries to replace
+some portion of the input token stream with <tt>error</tt> and then
+continue parsing.  For example, we might have productions such as:
+
+<pre><tt>    stmt ::= expr SEMI | while_stmt SEMI | if_stmt SEMI | ... |
+	     error SEMI
+	     ;</tt></pre>
+
+This indicates that if none of the normal productions for <tt>stmt</tt> can
+be matched by the input, then a syntax error should be declared, and recovery
+should be made by skipping erroneous tokens (equivalent to matching and 
+replacing them with <tt>error</tt>) up to a point at which the parse can 
+be continued with a semicolon (and additional context that legally follows a 
+statement).  An error is considered to be recovered from if and only if a 
+sufficient number of tokens past the <tt>error</tt> symbol can be successfully 
+parsed.  (The number of tokens required is determined by the 
+<tt>error_sync_size()</tt> method of the parser and defaults to 3). <p>
+
+Specifically, the parser first looks for the closest state to the top
+of the parse stack that has an outgoing transition under
+<tt>error</tt>.  This generally corresponds to working from
+productions that represent more detailed constructs (such as a specific
+kind of statement) up to productions that represent more general or
+enclosing constructs (such as the general production for all
+statements or a production representing a whole section of declarations) 
+until we get to a place where an error recovery production
+has been provided for.  Once the parser is placed into a configuration
+that has an immediate error recovery (by popping the stack to the first
+such state), the parser begins skipping tokens to find a point at
+which the parse can be continued.  After discarding each token, the
+parser attempts to parse ahead in the input (without executing any
+embedded semantic actions).  If the parser can successfully parse past
+the required number of tokens, then the input is backed up to the point
+of recovery and the parse is resumed normally (executing all actions).
+If the parse cannot be continued far enough, then another token is
+discarded and the parser again tries to parse ahead.  If the end of
+input is reached without making a successful recovery (or there was no
+suitable error recovery state found on the parse stack to begin with)
+then error recovery fails.
+
+<a name="conclusion">
+<h3>7. Conclusion</h3></a>
+
+This manual has briefly described the CUP LALR parser generation system.
+CUP is designed to fill the same role as the well known YACC parser
+generator system, but is written in and operates entirely with Java code 
+rather than C or C++.  Additional details on the operation of the system can 
+be found in the parser generator and runtime source code.  See the CUP
+home page below for access to the API documentation for the system and its
+runtime.<p>
+
+This document covers version 0.10j of the system.  Check the CUP home
+page:
+<a href="http://www.cs.princeton.edu/~appel/modern/java/CUP/">
+http://www.cs.princeton.edu/~appel/modern/java/CUP/</a>
+for the latest release information, instructions for downloading the
+system, and additional news about CUP.  Bug reports and other 
+comments for the developers should be sent to the CUP maintainer, 
+C. Scott Ananian, at
+<a href="mailto:cananian@alumni.princeton.edu">
+cananian@alumni.princeton.edu</a><p>
+
+CUP was originally written by 
+<a href="http://www.cs.cmu.edu/~hudson/">
+Scott Hudson</a>, in August of 1995.<p>
+
+It was extended to support precedence by 
+<a href="http://www.princeton.edu/~frankf">
+Frank Flannery</a>, in July of 1996.<p>
+
+On-going improvements have been done by
+<A HREF="http://www.pdos.lcs.mit.edu/~cananian">
+C. Scott Ananian</A>, the CUP maintainer, from December of 1997 to the
+present.<p>
+
+<a name="refs">
+<h3>References</h3></a>
+<dl compact>
+
+<dt><a name = "YACCref">[1]</a> 
+<dd>S. C. Johnson, 
+"YACC &emdash; Yet Another Compiler Compiler",
+CS Technical Report #32, 
+Bell Telephone Laboratories,  
+Murray Hill, NJ, 
+1975.
+
+<dt><a name = "dragonbook">[2]</a> 
+<dd>A. Aho, R. Sethi, and J. Ullman, 
+<i>Compilers: Principles, Techniques, and Tools</i>, 
+Addison-Wesley Publishing,
+Reading, MA, 
+1986.
+
+<dt><a name = "crafting">[3]</a> 
+<dd>C. Fischer, and R. LeBlanc,
+<i>Crafting a Compiler with C</i>,
+Benjamin/Cummings Publishing,
+Redwood City, CA,
+1991.
+
+<dt><a name = "modernjava">[4]</a>
+<dd>Andrew W. Appel,
+<i>Modern Compiler Implementation in Java</i>,
+Cambridge University Press,
+New York, NY,
+1998.
+
+</dl>
+
+<h3><a name="appendixa">
+Appendix A. Grammar for CUP Specification Files</a> (0.10j)</h3>
+<hr><br>
+<pre><tt>java_cup_spec      ::= package_spec import_list code_parts
+		       symbol_list precedence_list start_spec 
+		       production_list
+package_spec       ::= PACKAGE multipart_id SEMI | empty
+import_list        ::= import_list import_spec | empty
+import_spec        ::= IMPORT import_id SEMI
+code_part          ::= action_code_part | parser_code_part |
+                       init_code | scan_code
+code_parts         ::= code_parts code_part | empty
+action_code_part   ::= ACTION CODE CODE_STRING opt_semi
+parser_code_part   ::= PARSER CODE CODE_STRING opt_semi
+init_code          ::= INIT WITH CODE_STRING opt_semi
+scan_code          ::= SCAN WITH CODE_STRING opt_semi
+symbol_list        ::= symbol_list symbol | symbol
+symbol             ::= TERMINAL type_id declares_term |
+                       NON TERMINAL type_id declares_non_term |
+		       NONTERMINAL type_id declares_non_term |
+		       TERMINAL declares_term |
+		       NON TERMINAL declares_non_term |
+		       NONTERMIANL declared_non_term
+term_name_list     ::= term_name_list COMMA new_term_id | new_term_id
+non_term_name_list ::= non_term_name_list COMMA new_non_term_id |
+	               new_non_term_id
+declares_term      ::= term_name_list SEMI
+declares_non_term  ::= non_term_name_list SEMI
+precedence_list    ::= precedence_l | empty
+precedence_l       ::= precedence_l preced + preced;
+preced             ::= PRECEDENCE LEFT terminal_list SEMI
+	               | PRECEDENCE RIGHT terminal_list SEMI
+	               | PRECEDENCE NONASSOC terminal_list SEMI
+terminal_list      ::= terminal_list COMMA terminal_id | terminal_id 
+start_spec         ::= START WITH nt_id SEMI | empty
+production_list    ::= production_list production | production
+production         ::= nt_id COLON_COLON_EQUALS rhs_list SEMI
+rhs_list           ::= rhs_list BAR rhs | rhs
+rhs                ::= prod_part_list PERCENT_PREC term_id |
+                       prod_part_list
+prod_part_list     ::= prod_part_list prod_part | empty
+prod_part          ::= symbol_id opt_label | CODE_STRING
+opt_label          ::= COLON label_id | empty
+multipart_id       ::= multipart_id DOT ID | ID
+import_id          ::= multipart_id DOT STAR | multipart_id
+type_id            ::= multipart_id
+terminal_id        ::= term_id
+term_id            ::= symbol_id
+new_term_id        ::= ID
+new_non_term_id    ::= ID
+nt_id              ::= ID
+symbol_id          ::= ID
+label_id           ::= ID
+opt_semi	   ::= SEMI | empty
+
+</tt></pre>
+<hr><p><p>
+
+<h3><a name = "appendixb">Appendix B. A Very Simple Example Scanner<a></h3>
+<hr><br>
+<pre>
+<tt>// Simple Example Scanner Class
+
+import java_cup.runtime.*;
+import sym;
+
+public class scanner {
+  /* single lookahead character */
+  protected static int next_char;
+
+  /* advance input by one character */
+  protected static void advance()
+    throws java.io.IOException
+    { next_char = System.in.read(); }
+
+  /* initialize the scanner */
+  public static void init()
+    throws java.io.IOException
+    { advance(); }
+
+  /* recognize and return the next complete token */
+  public static Symbol next_token()
+    throws java.io.IOException
+    {
+      for (;;)
+        switch (next_char)
+	  {
+	    case '0': case '1': case '2': case '3': case '4': 
+	    case '5': case '6': case '7': case '8': case '9': 
+	      /* parse a decimal integer */
+	      int i_val = 0;
+	      do {
+	        i_val = i_val * 10 + (next_char - '0');
+	        advance();
+	      } while (next_char >= '0' && next_char <= '9');
+	    return new Symbol(sym.NUMBER, new Integer(i_val));
+
+	    case ';': advance(); return new Symbol(sym.SEMI);
+	    case '+': advance(); return new Symbol(sym.PLUS);
+	    case '-': advance(); return new Symbol(sym.MINUS);
+	    case '*': advance(); return new Symbol(sym.TIMES);
+	    case '/': advance(); return new Symbol(sym.DIVIDE);
+	    case '%': advance(); return new Symbol(sym.MOD);
+	    case '(': advance(); return new Symbol(sym.LPAREN);
+	    case ')': advance(); return new Symbol(sym.RPAREN);
+
+	    case -1: return new Symbol(sym.EOF);
+
+	    default: 
+	      /* in this simple scanner we just ignore everything else */
+	      advance();
+	    break;
+	  }
+    }
+};
+</tt></pre>
+
+
+<a name=changes>
+<h3>Appendix C:  Incompatibilites between CUP 0.9 and CUP 0.10</a></h3>
+
+CUP version 0.10a is a major overhaul of CUP.  The changes are severe,
+meaning no backwards compatibility to older versions.
+
+The changes consist of:
+<ul>
+<li> <a href="#lex_inter">A different lexical interface</a>,
+<li> <a href="#new_dec">New terminal/non-terminal declarations</a>,
+<li> <a href="#label_ref">Different label references</a>,
+<li> <a href="#RESULT_pass">A different way of passing RESULT</a>,
+<li> <a href="#pos_prop">New position values and propagation</a>,
+<li> <a href="#ret_val">Parser now returns a value</a>,
+<li> <a href="#prec_add">Terminal precedence declarations</a> and
+<li> <a href="#con_prec">Rule contextual precedence assignment</a>
+</ul>
+
+<h5><a name="lex_inter">Lexical Interface</a></h5>
+
+CUP now interfaces with the lexer in a completely different
+manner.  In the previous releases, a new class was used for every
+distinct type of terminal.  This release, however, uses only one class:
+The <tt>Symbol</tt> class.  The <tt>Symbol</tt> class has three instance
+variables which 
+are significant to the parser when passing information from the lexer.
+The first is the <tt>value</tt> instance variable.  This variable 
+contains the 
+value of that terminal.  It is of the type declared as the terminal type
+in the parser specification file.  The second two are the instance
+variables <tt>left</tt> and <tt>right</tt>.  They should be filled with 
+the <tt>int</tt> value of
+where in the input file, character-wise, that terminal was found.<p>
+
+For more information, refer to the manual on <a href="#lex_part">scanners</a>.
+
+<h5><a name="new_dec">Terminal/Non-Terminal Declarations</a></h5>
+
+Terminal and non-terminal declarations now can be declared in two
+different ways to indicate the values of the terminals or
+non-terminals.  The previous declarations of the form
+
+<pre><tt>
+terminal <i>classname terminal</i> [, <i>terminal ...</i>];
+</tt></pre> 
+
+still works.  The classname, however indicates the type of the value of
+the terminal or non-terminal, and does not indicate the type of object
+placed on the parse stack.
+
+A declaration, such as:
+
+<pre><tt>
+terminal <i>terminal</i> [, <i>terminal ...</i>];
+</tt></pre> 
+
+indicates the terminals in the list hold no value.<p>
+
+For more information, refer to the manual on <a
+href="#symbol_list">declarations</a>.
+
+<h5><a name="label_ref">Label References</a></h5>
+
+Label references do not refer to the object on the parse stack, as in
+the old CUP, but rather to the value of the <tt>value</tt> 
+instance variable of
+the <tt>Symbol</tt> that represents that terminal or non-terminal.  Hence,
+references to terminal and non-terminal values is direct, as opposed to
+the old CUP, where the labels referred to objects containing the value
+of the terminal or non-terminal.<p>
+
+For more information, refer to the manual on <a href="#label_part">labels</a>.
+
+<h5><a name="RESULT_pass">RESULT Value</a></h5>
+
+The <tt>RESULT</tt> variable refers directly to the value of the 
+non-terminal
+to which a rule reduces, rather than to the object on the parse stack.
+Hence, <tt>RESULT</tt> is of the same type the non-terminal to which 
+it reduces, 
+as declared in the non-terminal declaration.  Again, the reference is
+direct, rather than to something that will contain the data.<p>
+
+For more information, refer to the manual on <a href="#RES_part">RESULT</a>.
+
+<h5><a name="pos_prop">Position Propagation</a></h5>
+
+For every label, two more variables are declared, which are the label
+plus <tt>left</tt> or the label plus <tt>right</tt>.  These correspond 
+to the left and
+right locations in the input stream to which that terminal or
+non-terminal came from.  These values are propagated from the input
+terminals, so that the starting non-terminal should have a left value of
+0 and a right value of the location of the last character read.<p>
+
+For more information, refer to the manual on <a href="#label_part">positions</a>. 
+
+<h5><a name="ret_val">Return Value</a></h5>
+
+A call to <tt>parse()</tt> or <tt>debug_parse()</tt> returns a
+Symbol.  This Symbol is the start non-terminal, so the <tt>value</tt> 
+instance variable contains the final <tt>RESULT</tt> assignment. 
+
+<h5><a name="prec_add">Precedence</a></h5>
+
+CUP now has precedenced terminals.  a new declaration section,
+occurring between the terminal and non-terminal declarations and the
+grammar specifies the precedence and associativity of rules.  The
+declarations are of the form:
+
+<pre><tt>
+precedence {left| right | nonassoc} <i>terminal</i>[, <i>terminal</i> ...];
+...
+</tt>
+</pre>
+
+The terminals are assigned a precedence, where terminals on the same
+line have equal precedences, and the precedence declarations farther
+down the list of precedence declarations have higher precedence.  
+<tt>left, right</tt> and <tt>nonassoc</tt> specify the associativity 
+of these terminals.  left
+associativity corresponds to a reduce on conflict, right to a shift on
+conflict, and nonassoc to an error on conflict.  Hence, ambiguous
+grammars may now be used.<p>  
+
+For more information, refer to the manual on <a
+href="#precedence">precedence</a>.
+
+<h5><a name="con_prec">Contextual Precedence</a></h5>
+
+Finally the new CUP adds contextual precedence.  A production may be
+declare as followed:
+
+<pre><tt>
+lhs ::= <i>{right hand side list of terminals, non-terminals and actions}</i>
+        %prec <i>{terminal}</i>;
+</tt></pre>
+
+this production would then have a precedence equal to the terminal
+specified after the <tt>%prec</tt>.  Hence, shift/reduce conflicts can be
+contextually resolved.  Note that the <tt>%prec</tt> <i>terminal</i> 
+part comes after all actions strings.  It does not come before the 
+last action string.<p>
+
+For more information, refer to the manual on <a href="#cpp">contextual
+precedence</a>.
+
+These changes implemented by:
+<h3>
+<a href="http://www.princeton.edu/~frankf">Frank Flannery</a><br>
+<a href="http://www.cs.princeton.edu">Department of Computer Science</a><br>
+<a href="http://www.princeton.edu">Princeton University</a><br>
+</h3>
+<a name=bugs>
+<h3>Appendix D:  Bugs</a></h3>
+In this version of CUP it's difficult for the semantic action phrases (Java code attached
+to productions) to access the <tt>report_error</tt> method and other similar methods and
+objects defined in the <tt>parser code</tt> directive.
+<p>
+This is because the parsing tables (and parsing engine) are in one object (belonging to
+class <tt>parser</tt> or whatever name is specified by the <strong>-parser</strong> directive),
+and the semantic actions are in another object (of class <tt>CUP$actions</tt>).
+<p>
+However, there is a way to do it, though it's a bit inelegant.
+The action object has a <tt>private final</tt> field named
+<tt>parser</tt> that points to the parsing object.  Thus,
+methods and instance variables of the parser can be accessed within semantic actions as:
+<pre>
+    parser.report_error(message,info);
+    x = parser.mydata;
+</pre>
+<p>
+Perhaps this will not be necessary in a future release, and that
+such methods and variables as <tt>report_error</tt> and
+<tt>mydata</tt> will be available
+directly from the semantic actions; we will achieve this by combining the 
+"parser" object and the "actions" object together.
+ 
+<p>
+For a list of any other currently known bugs in CUP, see
+<A HREF="http://www.cs.princeton.edu/~appel/modern/java/CUP/bugs.html">
+http://www.cs.princeton.edu/~appel/modern/java/CUP/bugs.html</A>.
+
+<a name=version>
+<h3>Appendix E:  Change log</a></h3>
+
+<dl>
+<dt>0.9e<dd>March 1996, Scott Hudson's original version.
+<dt>0.10a<dd>August 1996, <a href="#about">several major changes</a> to
+the interface.
+<dt>0.10b<dd>November 1996, fixes a few minor bugs.
+<dt>0.10c<dd>July 1997, fixes a bug related to precedence declarations.
+<dt>0.10e<dd>September 1997, fixes a bug introduced in 0.10c relating
+to <tt>nonassoc</tt> precedence.  Thanks to 
+<a href="http://www.cs.purdue.edu/homes/hosking">Tony Hosking</a> 
+for reporting the bug and providing the fix.
+Also recognizes carriage-return character as white space and fixes a
+number of other small bugs.
+<dt>0.10f<dd>December 1997, was a maintenance release.  The CUP source
+was cleaned up for JDK 1.1.
+<dt>0.10g<dd>March 1998, adds new features and fixes old bugs.
+The behavior of RESULT assignments was normalized, and a problem
+with implicit start productions was fixed.  The CUP grammar was
+extended to allow array types for terminals and non-terminals, and
+a command-line flag was added to allow the generation of a symbol
+<i>interface</i>, rather than class.  Bugs associated with multiple
+invocations of a single parser object and multiple CUP classes in one 
+package have been stomped on.  Documentation was updated, as well.
+<dt>0.10h-0.10i<dd>February 1999, are maintenance releases.
+<dt>0.10j<dd>July 1999, broadened the CUP input grammar to allow more
+flexibility and improved scanner integration via the
+<code>java_cup.runtime.Scanner</code> interface.
+</dl>
+
+
+<hr>
+
+<a name="trademark">
+Java and HotJava are
+trademarks of <a href="http://www.sun.com/">Sun Microsystems, Inc.</a>,
+and refer to Sun's Java programming language and HotJava browser
+technologies.
+CUP is not sponsored by or affiliated with Sun Microsystems, Inc.
+
+<hr>
+
+
+</body></html>
-- 
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